i actually held a giant hairball like that (in a plastic bag) when i was in medical school. the pathology department had a collection of strange objects/organs, and the one i saw was the remains of a psych patients favorite teddy bear...apparently had a thing for pulling out the bear's fur and eating it. the hairball was rock hard and a perfect casting of the shape of her stomach. you could even see bits and pieces of a red ribbon tangled in the hair. needless to say, i've seen some pretty crazy stuff.
useless trivia...a ball of swallowed material (usually hair) that settles in the stomach like that is called a "bezoar." it's always been on my list of 'fun to say' medical terms